Displays in image display devices, such as television devices, are now being shifted from conventional cathode-ray tube displays to thin display panels, such as liquid crystal panels and plasma display panels. With the thin display panels, the thicknesses of the image display devices can be reduced. Liquid crystal panels included in liquid crystal display devices do not emit light, and thus backlight devices are required as separate lighting devices. The backlight devices are classified broadly into an edge-light type and a backlight type according to mechanisms. Edge-light type backlight devices are preferable for further reducing the thickness of liquid crystal display devices. An example of edge-light type backlight devices is disclosed in Patent Document 1.
In a backlight device according to Patent Document 1, an LED board on which LEDs are mounted is arranged opposite an end surface of a light guide plate and the LED board is attached to a heat dissipation member. The LEDs are light sources. Heat generated while the LEDs are turned on is transferred to the heat dissipation member via the LED board. This configuration is for promoting heat dissipation. The heat dissipation member includes two plate surfaces. One of the plate surfaces is parallel to an edge surface of the light guide plate and the LED board is mounted thereon. The other plate surface extends inward from an edge of the one of the plate surfaces of the heat dissipation member (i.e., toward the middle of the light guide plate) along the plate surface of the light guide plate. In this backlight device, efficiency in heat dissipation via the heat dissipation member is improved by increasing a dimension of the heat dissipation member.